After waking up, the desktop is visible for a short period before OS locks

## Prerequisites
- [x] I have searched open and closed issues for duplicates.

## Describe the bug
Occasionally, it takes some time before greeter shows up after waking up the computer. Before that, it is possible to control the desktop.

This doesn't happen every time – I tried to reproduce it to take a video right now, and I couldn't. However, it happened to me cca. five times over the last week.

### To Reproduce
Steps to reproduce the behavior:
1. Put the computer to sleep mode
2. Wake it up
3. Sometimes, the desktop shows up, with all the applications that are opened
4. If you're lucky, you can do an action (eg. close an window) without unlocking
5. After a short period (≈1 sec), the greeter shows up, requesting the password

### Expected behavior
After waking up from sleep, **no action** should be possible without knowing the password.

### Screenshots or screen recordings
Not yet, sadly.

## Platform Information
- [x] I'm using the latest released stable version